Amplifier with heater compensation



Aug. 3o, 1949.

l.. P. PARADISE E'rfAL 2,480,418

AMPLIFIER WITH HEATER COMPENSATION Filed May 4, 1944 Patented Aug. 30, 1949 TENT" AuerbachergBrooklyn, N.

Television Institute;v Inc., New' Yfork; -N2 'EL az: corporation of- NewfYork 5"Claims; (Cl.

The invention'lrelates itoria`compensatingmeansl or circuit which compensatesfor variationsinY l'ieatervolt'age of-V an amplier tube. The cathode heater ofi a tube isA customarily connectedV with a-'transorm'er to suppl-y theenergyior the heater. 5 If there are changes-2 in tl-ieesupplyl voltagefthe heater becomes -hotter or colder dependinglupont the'Varia-tion and'consequentlyfcauses an increaseor-l decrease: in electronic emissionv from thecathode ancl'infthe' current-through'the tube.' In or- 10 derJ tof. compensate for' such variations inf-heater or cathode voltage the compensating-f circuit is! used so that the ampli-fierl tube'is Vinsensitivelt variations in heatervoltages.

It is'anobject-of-theinvention to construct'a 15l new and-novel circuit` which compensates for variations of the-*heater Voltageoffthe"tube.

Anotherv obj ect is toconstructa circuit WhichJ compensates for variationsv of'heatervoltage by varying the voltage up'onafgrid of the tubelin 20v" accordance withvvari'ations in heater voltagel or temperature so that the amplifying tube is--in'- sensitive to' heater Variations.'-

A stillfurtherl` obiectl of 'the invention-iisl'to` constructy aV compensating circuit or means' in'` 25 which` variations in thel heater Voltagekproduceif a" corresponding variation in the voltage applied?v tothe screen grid-of-a .pentode amplifier.'

Other objectsof the' invention Will be more apparent from the" followingl description".takenA 30 iny connection with: thef accompanying drawingswhich illustrate two embodiments thereof in*v Whichf- Figure 1 shows aL diagrammatic circuit'illistrating an amplifier 'tube and `'acontrol tube fr` 35 varying thepotential applied.- to the screen grid'- of the amplifier tubeasfthe'heatervoltage varies- Figure 2 showsa diagrammatic circuit utiliz-vr ing a triode as the amplifying tube:

The compensating' circuit of Figure l-includes 40' anamplier tube-'I0 having at least a pair of grid electrodes, the tube illustrated being a pen-1 tode having a plate or anode l I-, screenlgrd" |22 control grid I3, a suppressor gri'd"II, cathod'eflf and the cathode l heater I5iA A resistance |6345" provides impedance means connected to:l the." anode of' the-tube' to provide-a load therefores'- The resistance I6 is connected with the high potential lsideVA off-a vD. C. supply voltage. The outputvcircuit connection' or terminals are con-fr nectedy across the-resistance I6, that' is lbetw'eenf" the anode I-Iv'of the tube IIJ anda^poir-1t^offiikedfl or "substantially fl-Xed'" lpotntial'. The fin-putter minalsorconnectionl apply the' signalft'o 'the contror'grd 'I3 as willv appearhereinafter.A

introduce ane undesireinneasdvoltage drop@ throughi l-i'e resistor-1116. Iniorderfwt compensate@ |ugitheftobezutfwn1enmay-.berdesignatd a tapan provided.:anaosmrfthsilavter tubefisir orf-anode -currenewnn-tne-sam inereasefifneateei volta-gef- 'rnisfinerasediefenttarea@ feinste? 20 will result in an increased potentialtl equivalent to the increase caused by the increased tei-iperature and increased emission of the cathode, and hence compensate for the tendency to increase the current occasioned by the increased heater voltage.

In Figure 2 a circuit is illustrated in which the amplifying tube is a triode. Corresponding parts are numbered similarly to Figure 1 and need not be again described. It should be noted however, that the compensating tube is connected with the negative side of the voltage supply rather than to the voltage divider as illustrated in Figure 1. In other words the compensating tube and its anode resistance preferably shunts the entire voltage divider 3U, 3| when a triode is used as the amplifying tube.

The amplifying tube has a cathode 4l, control grid 42 and anode 43. The tube illustrated has an indirectly heated cathode and hence is heated by a cathode heater 44. The heaters of both tubes are connected with the same source of current supply. Since the amplifying tube is a three element tube, the anode circuit of the compensating tube 20 is connected by the connection 45 with the control grid 42. The connection preferably is with the plate 2| of the compensating tube. A resistance 46 is also connected with the control grid which for A. C. amplification, may be substituted by a condenser.

The compensating circuit illustrated in Figure 2 operates in the same manner that the circuit of Figure 1 operates except that the voltage to compensate for heater variation is applied directly to the control grid of the amplifying tube rather than to a screen grid.

This invention is presented to fill a need for improvements in a compensating circuit. It is understood that various modifications in structure, as well as changes in mode of operation, assembly, and manner of use, may and often do occur to those skilled in the art, especially after beneflting from the teachings of an invention. Hence, it will be understood that this disclosure is illustrative of preferred means of embodying the invention in useful form by explaining the construction, operation and advantages thereof.

What is claimed is:

1. A heater compensating amplifier circuit comprising a voltage divider adaptedto be connected across a source of D. C. Voltage; a first space discharge tube having a cathode, control grid and anode, a bias resistance in series with the cathode, a connection between the control grid and the 10W potential side of the bias resistance which is its sole connection, a resistance connected with the anode of said tube, and the tube and resistance connected in shunt with at least a portion of the voltage divider; a second space discharge tube having a cathode, control grid, a screen grid and an anode, an output circuit connected with the anode of the second tube and a point of fixed potential; means connecting together the cathode heaters of both tubes for supply from the same source of heater current; a D. C. conducting connection from the anode of the first tube to the screen grid of the second tube, and input connections for the second tube between the control grid and the cathode whereby plate current of the second tube is rendered substantially free from changes in cathode emission.

2. A heater compensating amplifying circuit comprising a voltage divider adapted to be connected across a source of D. C. voltage; a rst space discharge tube having a cathode, and

'4 anode, a resistance connected with the anode of the rst tube, the tube and the resistance being connected in shunt with at least a portion of the voltage divider, and the cathode of the tube being connected at a point spaced from the low potential side of the voltage divider; a second space discharge tube having a cathode, control grid, a screen grid and an anode, an output circuit for the second tube, and the output circuit and second tube being connected across a portion of the voltage divider, the cathode of the tube being connected at a point spaced from the low potential side of the voltage divider; means connecting together the cathode heaters of both tubes for supply from the same source of heater current; a D. C. conducting connection from the anode of the first tube to the screen grid of the second tube; and input connections with the ccnrol grid of second tube and the low potential side f of the voltage divider whereby plate current of the second tube is rendered substantially free from changes in cathode emission.

3. A heater compensating amplifying circuit comprising a voltage divider adapted to be connected across a source of D. C. voltage; a, rst space discharge tube having a cathode, control grid and anode, a resistance connected with the anode of the rst tube, a bias resistance connected with the cathode, a connection between the control grid and the low potential end of the bias resistance which is its sole connection, the tube and the resistances being connected in shunt with at least a portion of the voltage divider, and the cathode of the tube being connected at a point spaced from the low potential side of the voltage divider; a, second space discharge tube having a cathode, control grid, a screen grid and an anode, an output circuit for the second tube, and the output circuit and second tube being connected across a portion of the voltage divider, the cathode of the tube being connected at a point spaced from the low potential side of the voltage divider; means connecting together the cathode heaters of both tubes for supply from the same source of heater current; a D. C. conducting connection from the anode of the first tube to the screen grid of the second tube; and input connections with the control grid of the second tube and the low potential side of the voltage divider whereby plate current of the second tube is renr cathode, control grid and anode, a resistance connected with the anode of the first tube and adapted to be connected with a source of D. C. voltage, a bias resistance connected with the cathode of the first tube, and a connection from the control grid to the low potential side of the bias resistance and being the sole connection therebetween, a second space discharge tube having a cathode, control grid, screen grid, and an anode, a resistance connected with the anode of the second tube and adapted to be connected with a source of D. C. potential, the cathode of the second tube being connected with the low potential side of the bias resistance of the first tube; bias means connected with the cathode of the second tube and in series with the bias resistance of the first tube; means connecting together the cathode heaters of both tubes for supply from the same source of heater current; a D. C. conducting connection from the anode of the first tube to the screen `grid of the second tube; and input connections with the control grid of the second tube and the bias means whereby plate current of the second tube is rendered substantially free from changes in cathode emission.

5. A heater compensating amplifying circuit comprising a voltage divider adapted to be connected across a source of D. C. voltage; a rst space discharge tube having a cathode, control grid and anode, a resistance connected with the anode o the rst tube and with the high potential end of the voltage divider, a bias resistance connected with the cathode of the tube and at a point spaced from the low potential side of the voltage divider, and the control grid being connected solely with the low potential side of the bias resistance; a second space discharge tube having a cathode, control grid, a screen grid, a suppressor grid and an anode, an output circuit connected with the anode of the second tube and with the high potential side of the voltage divider, the cathode of the second tube being connected with the voltage divider at the same point that the bias resistance of the first tube is connected therewith; means connecting together the cathode heaters of both tubes for supply from the same source of heater current; a D. C. conducting connection from the anode of 'the first tube to the screen grid of the second tube; and input connections with the control grid of the second tube and the low potential side of the voltage divider whereby plate current of the second tube is rendered substantially free from changes in cathode emission.

LIONEL P. PARADISE.

WERNER F. AUERBACHER.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS 

